In the recent drive for higher integration and operating speeds in LSI devices, the pattern rule is made drastically finer. Active efforts have been made on the development of microfabrication technology using deep ultraviolet (deep UV) and extreme ultraviolet (EUV) lithography. The photolithography using KrF excimer laser (wavelength 248 nm) and ArF excimer laser (wavelength 193 nm) as the light source has already established the main role in the commercial manufacture of semiconductor devices. The photolithography relying on the liquid immersion technique for implementing further miniaturization has been practiced in the commercial manufacture. While EUV and EB are considered promising for the next generation photolithography, a number of problems must be overcome before the manufacture technology can enter the commercial phase of semiconductor device production.
As the approach for improving the resolution from the aspect of photoresist film, a variety of techniques have been developed including the employment of chemically amplified reaction scheme, the addition of acid quenchers, contrast enhancement by an acid-labile leaving group requiring higher activation energy, and resolution enhancement by an acid-labile leaving group of lower activation energy in low optical image contrast regions. See Patent Documents 1 and 2.
Since a limit is foreseen in the continuing trend for shorter wavelength in the photolithography, a demand for a photoresist film having a further improved resolution is increasing toward the goal of manufacturing finer size devices at lower costs by the universal KrF and dry ArF lithography techniques.